1 //===- StreamableMemoryObject.h - Streamable data interface -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 #ifndef STREAMABLEMEMORYOBJECT_H_
12 #define STREAMABLEMEMORYOBJECT_H_
14 #include "llvm/ADT/OwningPtr.h"
15 #include "llvm/Support/Compiler.h"
16 #include "llvm/Support/MemoryObject.h"
17 #include "llvm/Support/DataStream.h"
22 /// StreamableMemoryObject - Interface to data which might be streamed.
23 /// Streamability has 2 important implications/restrictions. First, the data
24 /// might not yet exist in memory when the request is made. This just means
25 /// that readByte/readBytes might have to block or do some work to get it.
26 /// More significantly, the exact size of the object might not be known until
27 /// it has all been fetched. This means that to return the right result,
28 /// getExtent must also wait for all the data to arrive; therefore it should
29 /// not be called on objects which are actually streamed (this would defeat
30 /// the purpose of streaming). Instead, isValidAddress and isObjectEnd can be
31 /// used to test addresses without knowing the exact size of the stream.
32 /// Finally, getPointer can be used instead of readBytes to avoid extra copying.
33 class StreamableMemoryObject : public MemoryObject {
35 /// Destructor - Override as necessary.
36 virtual ~StreamableMemoryObject();
38 /// getBase - Returns the lowest valid address in the region.
40 /// @result - The lowest valid address.
41 virtual uint64_t getBase() const = 0;
43 /// getExtent - Returns the size of the region in bytes. (The region is
44 /// contiguous, so the highest valid address of the region
45 /// is getBase() + getExtent() - 1).
46 /// May block until all bytes in the stream have been read
48 /// @result - The size of the region.
49 virtual uint64_t getExtent() const = 0;
51 /// readByte - Tries to read a single byte from the region.
52 /// May block until (address - base) bytes have been read
53 /// @param address - The address of the byte, in the same space as getBase().
54 /// @param ptr - A pointer to a byte to be filled in. Must be non-NULL.
55 /// @result - 0 if successful; -1 if not. Failure may be due to a
56 /// bounds violation or an implementation-specific error.
57 virtual int readByte(uint64_t address, uint8_t* ptr) const = 0;
59 /// readBytes - Tries to read a contiguous range of bytes from the
60 /// region, up to the end of the region.
61 /// May block until (address - base + size) bytes have
62 /// been read. Additionally, StreamableMemoryObjects will
63 /// not do partial reads - if size bytes cannot be read,
64 /// readBytes will fail.
66 /// @param address - The address of the first byte, in the same space as
68 /// @param size - The maximum number of bytes to copy.
69 /// @param buf - A pointer to a buffer to be filled in. Must be non-NULL
70 /// and large enough to hold size bytes.
71 /// @param copied - A pointer to a nunber that is filled in with the number
72 /// of bytes actually read. May be NULL.
73 /// @result - 0 if successful; -1 if not. Failure may be due to a
74 /// bounds violation or an implementation-specific error.
75 virtual int readBytes(uint64_t address,
78 uint64_t* copied) const = 0;
80 /// getPointer - Ensures that the requested data is in memory, and returns
81 /// A pointer to it. More efficient than using readBytes if the
82 /// data is already in memory.
83 /// May block until (address - base + size) bytes have been read
84 /// @param address - address of the byte, in the same space as getBase()
85 /// @param size - amount of data that must be available on return
86 /// @result - valid pointer to the requested data
87 virtual const uint8_t *getPointer(uint64_t address, uint64_t size) const = 0;
89 /// isValidAddress - Returns true if the address is within the object
90 /// (i.e. between base and base + extent - 1 inclusive)
91 /// May block until (address - base) bytes have been read
92 /// @param address - address of the byte, in the same space as getBase()
93 /// @result - true if the address may be read with readByte()
94 virtual bool isValidAddress(uint64_t address) const = 0;
96 /// isObjectEnd - Returns true if the address is one past the end of the
97 /// object (i.e. if it is equal to base + extent)
98 /// May block until (address - base) bytes have been read
99 /// @param address - address of the byte, in the same space as getBase()
100 /// @result - true if the address is equal to base + extent
101 virtual bool isObjectEnd(uint64_t address) const = 0;
104 /// StreamingMemoryObject - interface to data which is actually streamed from
105 /// a DataStreamer. In addition to inherited members, it has the
106 /// dropLeadingBytes and setKnownObjectSize methods which are not applicable
107 /// to non-streamed objects.
108 class StreamingMemoryObject : public StreamableMemoryObject {
110 StreamingMemoryObject(DataStreamer *streamer);
111 virtual uint64_t getBase() const LLVM_OVERRIDE { return 0; }
112 virtual uint64_t getExtent() const LLVM_OVERRIDE;
113 virtual int readByte(uint64_t address, uint8_t* ptr) const LLVM_OVERRIDE;
114 virtual int readBytes(uint64_t address,
117 uint64_t* copied) const LLVM_OVERRIDE;
118 virtual const uint8_t *getPointer(uint64_t address,
119 uint64_t size) const LLVM_OVERRIDE {
120 // This could be fixed by ensuring the bytes are fetched and making a copy,
121 // requiring that the bitcode size be known, or otherwise ensuring that
122 // the memory doesn't go away/get reallocated, but it's
123 // not currently necessary. Users that need the pointer don't stream.
124 assert(0 && "getPointer in streaming memory objects not allowed");
127 virtual bool isValidAddress(uint64_t address) const LLVM_OVERRIDE;
128 virtual bool isObjectEnd(uint64_t address) const LLVM_OVERRIDE;
130 /// Drop s bytes from the front of the stream, pushing the positions of the
131 /// remaining bytes down by s. This is used to skip past the bitcode header,
132 /// since we don't know a priori if it's present, and we can't put bytes
133 /// back into the stream once we've read them.
134 bool dropLeadingBytes(size_t s);
136 /// If the data object size is known in advance, many of the operations can
137 /// be made more efficient, so this method should be called before reading
138 /// starts (although it can be called anytime).
139 void setKnownObjectSize(size_t size);
142 const static uint32_t kChunkSize = 4096 * 4;
143 mutable std::vector<unsigned char> Bytes;
144 OwningPtr<DataStreamer> Streamer;
145 mutable size_t BytesRead; // Bytes read from stream
146 size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header)
147 mutable size_t ObjectSize; // 0 if unknown, set if wrapper seen or EOF reached
148 mutable bool EOFReached;
150 // Fetch enough bytes such that Pos can be read or EOF is reached
151 // (i.e. BytesRead > Pos). Return true if Pos can be read.
152 // Unlike most of the functions in BitcodeReader, returns true on success.
153 // Most of the requests will be small, but we fetch at kChunkSize bytes
154 // at a time to avoid making too many potentially expensive GetBytes calls
155 bool fetchToPos(size_t Pos) const {
156 if (EOFReached) return Pos < ObjectSize;
157 while (Pos >= BytesRead) {
158 Bytes.resize(BytesRead + BytesSkipped + kChunkSize);
159 size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped],
162 if (bytes < kChunkSize) {
163 if (ObjectSize && BytesRead < Pos)
164 assert(0 && "Unexpected short read fetching bitcode");
165 if (BytesRead <= Pos) { // reached EOF/ran out of bytes
166 ObjectSize = BytesRead;
175 StreamingMemoryObject(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION;
176 void operator=(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION;
179 StreamableMemoryObject *getNonStreamedMemoryObject(
180 const unsigned char *Start, const unsigned char *End);
183 #endif // STREAMABLEMEMORYOBJECT_H_